The advantages of magnetic media for storing information are well known. These advantages include the ability to write data or information to the magnetic storage medium, to read the data, to erase the data, and to write either the same or different data for storage. Rotating floppy discs exemplify one form of magnetic storage medium; such a disc may be rotated past the read/write head of a disc drive which writes or reads information on the disc. Fixed disc or hard disc magnetic storage media also are known; due to the greater precision and controls thereof and to other factors the fixed or hard disc systems usually are capable of storing more data than can be stored on a single or a small number of floppy discs.
As used herein the terms data and information may be interchanged as synonyms. Ordinarily, though, information may represent or may be represented by a logic one or a logic zero signal or condition, e.g. the on or off condition of a switch; and data is the assemblage of information. These rules and definitions, though, may not be strictly adhered to herein.
Various optical systems for storing data and permitting reading out of the data, e.g. using a laser and photodetector optics, also are known. One example is the laser disc system used for video signal storage and another is the so-called compact disc typically used for music. One drawback to such optical systems has been the inability to erase information stored in the optical storage medium and especially to erase and then again to write information to the storage medium for subsequent storage.